MORELIA, Mexico (AP) — Gunmen ambushed and killed one of Mexico’s highest ranking navy officials and the officer escorting him Sunday in the rough western state of Michoacan, authorities said. Two other people were injured in the shooting in an area where a fight between rival drug cartels has caused a new outburst of violence.

The state prosecutors’ office said the attack on Vice Adm. Carlos Miguel Salazar happened on a dirt road near the town of Churintzio. The motive was unclear, but Salazar is the top navy commander in the neighboring Pacific coastal state of Jalisco.

Attacks by Mexican cartels on military personnel have occurred, but are relatively rare. Salazar may be the highest military officer slain since the government began an offensive against the cartels in late 2006.

Navy officials would not confirm whether Salazar was on duty Sunday. Marines are known to carry out operations in Michoacan, but in a smaller capacity than the federal police and army.

Alejandro Arellano, spokesman for Michoacan attorney general’s office, said Salazar’s driver apparently took the dirt road because the main highway had been closed. He said Ricardo Fernandez Hernandez, an officer serving as the admiral’s bodyguard, was also killed. Arellano said a woman and another man traveling in the car were injured.

A statement from the Mexican navy said the commander’s SUV was traveling on a main highway that connects Morelia, Michoacan’s capital, to the city of Guadalajara and farther west to Salazar’s navy base. The vehicle was forced to take a detour near Churintzio and men armed with high-powered rifles opened fire while it was between two villages, the statement, it said.

Helicopters of the army, navy and federal police and more than 200 security officers and emergency workers converged on the scene after the shooting. The attackers had not been located, but officials said forces searching the area found an abandoned car suspected of being used by the gunmen.

The navy is considered the most successful Mexican force in the drug war, with marines proving to be the best trained and least corruptible. Marines killed the head of the Beltran Leyva cartel in the city of Cuernavaca in 2009 and captured Zetas cartel leader Miguel Angel Trevino near the U.S.-Mexico border two weeks ago.

Navy officers have rarely been targeted by the gangs despite clearly setting their eyes on drug criminals. In August 2011, nine Mexican marines were abducted.

Other top officials have died, such as Edgar Millan, who was the acting head of the police before he was gunned down in 2008 inside his Mexico City home, possibly in retaliation for investigating drug trafficking at the airport.

The government has tried to bring down homicides related to drug fights, and recently scored a victory with the capture of Trevino, who was feared by many for the Zetas’ brutal killings of migrants and scary tactics on foes. But the fight in Michoacan is heating up and proving to be President Enrique Pena Nieto’s main security challenge.

Since Tuesday, gunmen apparently working for the Knights Templar cartel have been staging a series of attacks on federal police convoys, killing at least four officers and wounding five others. The death toll from the clashes also included 20 gunmen. Authorities said gunmen have hijacked trucks and buses to block highways before making their attacks.

Pena Nieto sent thousands of troops and federal police to the area two months ago because of a surge in violence stemming from a reported fight between the Knights Templar and a gang called the New Generation, based in neighboring Jalisco state. Vigilante groups have also been sprouting up this year, and regular citizens have staged demonstrations demanding more protection.